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Mike;I too was hunting down a ghost wiring issue "no start after engine gets hot". I chased everything, grounds, resistance wires. Bottom line I changed the under-hood headlight harness and engine harness with the engine in. Had to snake it in a few places otherwise worked fine. Never could isolate the resistance issue. I imagine buried somewhere in the harness is a burnt wire that goes open or drastically increases resistance after running and hot. I know you might not want to hear this but if I had to do it again, I'd buy new harnesses and just replace them. No use burning a car to the ground for want of a good harness. Now I know yours is not that drastic however the electrical harnesses are 47 years old. I would also recommend if you can't find the issue and are on a budget remove the harnesses unwrap them and troubleshoot yourself.

8 volts is marginal to get a starter motor solenoid to operate. They will hold in on less than that once operated.You should have at least 10 volts at the solenoid purple wire to guarantee it will operate.Some volts are still being lost somewhere.

You don't need 2 guys to check the solenoid. Once it doesn't start just tap with a screw driver on the solenoid a couple of times. Sometimes a solenoid will stick, and over time will pop back open . So when you go back to the car all of sudden the problem is gone. I have had this happen as a result of running headers to close to the solenoid, and it getting to hot. Example I drove my 66 Chevelle 20 minutes, would park it, and then come back out like 5 minutes later, and it would not turn over. I would either have to wait 15 minutes for it to cool down and un stick, or tap on the solenoid, and presto it would turn over and start up. Once I figured it out I ran a heat shield over the starter and that solved it. This may not be your solution, but it may eliminate it as a possibility.

Try this as well when it doesn't start and I guess you are actually saying no crank? - hook up your remote starter switch if she cranks your issue is within the column ignition/NSS/to coil wiring circuit.

Try this as well when it doesn't start and I guess you are actually saying no crank? - hook up your remote starter switch if she cranks your issue is within the column ignition/NSS/to coil wiring circuit.

I'm thinking that it is in teh bulkhead connector but I've already re3moved it and cleaned teh connections and it looks to be in pretty good shape. I'm getting ready to add a solid state relay at the starter as I've seen other's do.

Engine Ground to frame and body? Corrosion at firewall fuseblock connection? (sorry, think you said you cleaned this already-put some dielectric grease on contacts to pevent further problems)Reverse lockout switch circuitry, connections, or adjustment of linkage or no linkage causing column to lose contact intermitently.

Engine Ground to frame and body? Corrosion at firewall fuseblock connection? (sorry, think you said you cleaned this already-put some dielectric grease on contacts to pevent further problems)Reverse lockout switch circuitry, connections, or adjustment of linkage or no linkage causing column to lose contact intermitently.

The battery is grounded directly to the engine block via water pump bolt and there is a wire from the negative battery post to the front right fender. I do not have a ground strap from the engine to the body.

If I'm understanding you right when it fails you have 8 volts. Are you sure you have the wiring correct? Maybe the resistor coil wire hook to the solenoid?

This is what I'm thinking now but based on my last test I think that it may be the under dash wiring harness. I just removed the fuse box and separated it's two halves so that I can put a volt meter on the red wire coming into the passenger compartment and the purple wire leaving the engine compartment and I don't remember the exact numbers but I think that I was getting over 11vdc in and about 9vdc out teh purple. There is a substantial voltage drop between the bulkhead connector wire in and the on that goes back out to the starter.

I too was hunting down a ghost wiring issue "no start after engine gets hot". I chased everything, grounds, resistance wires. Bottom line I changed the under-hood headlight harness and engine harness with the engine in. Had to snake it in a few places otherwise worked fine. Never could isolate the resistance issue. I imagine buried somewhere in the harness is a burnt wire that goes open or drastically increases resistance after running and hot. I know you might not want to hear this but if I had to do it again, I'd buy new harnesses and just replace them. No use burning a car to the ground for want of a good harness. Now I know yours is not that drastic however the electrical harnesses are 47 years old. I would also recommend if you can't find the issue and are on a budget remove the harnesses unwrap them and troubleshoot yourself.

and my reply

This is what I'm thinking now but based on my last test I think that it may be the under dash wiring harness. I just removed the fuse box and separated it's two halves so that I can put a volt meter on the red wire coming into the passenger compartment and the purple wire leaving the engine compartment and I don't remember the exact numbers but I think that I was getting over 11vdc in and about 9vdc out the purple. There is a substantial voltage drop between the bulkhead connector wire in and the one that goes back out to the starter.

Try this as well when it doesn't start and I guess you are actually saying no crank? - hook up your remote starter switch if she cranks your issue is within the column ignition/NSS/to coil wiring circuit.

How did you correct it from sticking?

It's not always a 'sticking' problem in the true sense of the word. It can be, but not usually.This particular solenoid design has a 'snap action', they're either fully released or fully operated.

When the magnetic flux in the armature [the moving part] reaches 'critical mass', the armature begins to move.This movement causes the flux to increase even further and it's 'game over'. The armature will continue to move, causing ever increasing flux until it is fully operated.

So there's a very tight threshold voltage/current which when reached, causes the armature to snap from fully released to fully operated.If there is sufficient losses in the wiring/connections causing the solenoid to not operated, it may be that the voltage is only just below the critical operate point.

When you tap the solenoid you can cause a couple of different things to happen which on their own or in combination, may be just enough to get the armature to move when you turn the key to start.You can cause a slightly better connection at either the purple wire, or slightly improved earthing of the solenoid case to the nose cone, or even a slightly better connection of the main terminal on the starter motor side [important for dual winding solenoids]. Any of which may cause a few extra milliamps to flow and get the solenoid over the operate threshold.

The other thing is that the tapping may just jostle the armature a bit and cause a slight drop in sliding friction - you've lowered the operate threshold.

With regard to heat, yes, this can be a problem. It causes increasing resistance in the solenoid windings = less current = less flux = maybe not enough to operate anymore.But imo, most of the time it is simply exacerbating a problem elsewhere. If you have at least 10 volts on the solenoid wire the instant you rotate the key to start, the solenoid should still operate, though I must admit, that close proximity to headers may be a bit too much of a flaming for any system to put up with, no matter how good everything else is.

Try installing a temporary heat shield between the header and starter. The close proximity sometimes destroys the internals of both starters and solenoids. Cheap thermal insulation should do the trick.

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Barry Old guy but still learning.....Unrestored 67 barn find67 SS 350 in process ( in paint booth now)Looking for N243673 to reunite V0320MO block and crank